Conversion of hydrocarbon oils



Jan. L. Q HUFF CONVERSION OF HYDROCARBON OILS Filed Aug. 28., 1957 mmuumm, wh

HUHIIII INVENTOR LYMAN C. HUFF ATTORNEY Patented Jan. 27, 1942 UNIT-Eo STATES PATENT "OFFICE l i' i n* 2,271,298 l. coNvEnsioNor nYnRocAoN ons. ALyman C# Huff, 1 Chicago, ,111., assigner to Universal `Oil Products Company-,Chicago,`1ll., a.` `corporation of Delaware A I f Application August as, 1937, serial No. 161,402

s claims; A. (c1. 19t-iis.)

This is a continuationrin-part of my cospendingv application Serial No. 113,424, filed November 30, 1936. i y

This invention relates toimprovements in the `type of process wherein hydrocarbon oil/S are pyrolytically converted to produce high yields of good antiknock gasoline and more specifically to a process wherein oils boiling above lthe range of gasoline are cracked to produce high yields of gasoline boiling range materials, the

latterseparated into light and heavy fractions andsaid heavy gasoline fractions` reformed undercracking conditions of elevated temperature and superatmospheric pressure to materially improve their antiknock value',

One specific embodimentof the invention comprises cracking an oil of higher boiling characteristics than gasoline to produce therefrom high yields of gasoline boiling range materials, fractionating the resultant cracked vaporous products to separate therefrom, as refluxv con.-y densate, components boiling abovethe range of gasoline, returning said reflux condensate to 'further cracking Within the system, further fractionating the uncondensed vapors, compris.- f

ing predominantly materials within the boiling range ofr gasoline, to separate` the same into low-boiling vaporous components` comprising light gasoline fractions of satisfactory anti'- knock Value and a higher boiling condensate" comprising heavy gasoline fractions 'of 'unsatisfactory antiknock value, condensing and recovering said light gasoline fractions as a' portion of the final motor fuel product of the process, subjecting said higher boiling condensate to cracking conditions ofelevated temperature and superatmospheric pressure adequate to produce therefrom high yields of gasoline of irnproved antiknock value, separating'vapors'eand non-vaporous residual components of lthefproduct's of the last mentioned cracking operation, fractionating the last mentioned vapors outy of 'contact with the vaporousproducts undergoing fractionation in the aforementioned .fractionf Q cracking operation.

The present invention is not directed .to

Aoline fractions subjected to the last mentionedv specific, single feature of the ,above described process but is believed to reside in the cooperative combination of featureswhich result in the recovery, .Without further cracking, of those low-boiling gasoline fractions produced in the initial cracking operation which are of satisfae tory antiknock Value rand further converSOIl of those higher boiling gasoline fractions produced in the initial cracking operation which 'are of unsatisfactory antiknock value to convert the same into high yields of a wider boiling range gasoline of materially improved antiknock value.

The invention also provides, as a special feature thereof, for the use, in addition to the charging stock supplied to theinitial cracking operation, of .a secondary charging-stock such as gasoline .or a distillate of substantially gasoline boiling range from an external sourcer vand which contains bothlloW-boiling gasoline lfractions of satisfactory antiknock value and higher boiling gasoline' fractions of inferior antiknock value. This material may be suppliedto the first or to the second mentioned fractionating step of the systemand directly eommingled therein with the vaporous conversion products of the process undergoing fractionation in this -zone whereby itscomponentsfof gasoline boiling range are separated, together with the gasoline conversion products of theinitial cracking operation, into selected ,low-boiling and high-boiling fractions which are, respectively, recovered as a portion of the nalymotor-fuel product andireformed or cracked to produce gasoline of improved antiknock value. 1

Another feature of the invention resides in the usewof reflux condensate formed in the frac.-

lti'onating vstep ofthe 'reforming system as a heat exchange medium forfreheating and/or reboiling the condensate supplied to said reforming step and/or as a cooling and fra'ctionating medium in the initial fractionating step of the system.

[The above mentioned*y and other features and advantages of the invention will be fully described and Iexplained in conjunction with the lwhich .relatively heavy oil consisting predominantly -of materials boiling above the range of gasoline is supplied, as will be later described, forl cracking, is supplied with sufficient vheat by means of furnace 2 ito heat the oil passing vaporous components are afforded appreciable additional cracking in this Zone. The resultant vaporous and liquid conversion products are withdrawn, in the particular case here illustrated, in commingled state from thelower portion of distillate bottoms and the like.

chamber 5 and directed therefrom through line- 6 and valve 1 into vaporizlng and separating chamber 8.

Chamber 8 is preferably operated at a substantially reduced pressure relative to that employed inthe reaction chamber by means of which appreciable further vaporization of the liquid conversion products supplied thereto is accomplished. Separation of vapors and non-vaporous residue is accomplished in chamber 8 and, when this Zone -is operated for the production of liquid residue as a final product of the process, the latter may be removed from the lower portion thereof and directed through line 9 and valve I0 to cooling and storage or elsewhere, as desired.

The vaporous products are directed from the upper portion of chamber 8 through line II and valve I2 to fractionation in fractionator I3 wherein all or at least a major portion of their components boiling above the range of gasoline are condensed as reflux condensate. The total reflux condensate formed in fractionator I3 or selected high-boiling fractions thereof, as desired, are directed from the lower portion of this zone through line I4 and valve I5 to pump I6 by means of which they are supplied through line I'I and valve I8 to conversion, as previously described, in heating coil I.

Although the invention is not so limited, it is ordinarily preferable to separate the reflux condensate formed in fractionator I3 into selected relatively low-boiling and high-boiling fractions, in which case only the high-boiling fractions are supplied, as previously described, to heating coil I while thel lower boiling fractions may be recovered, all or in part, as a nal product of the process, or'preferably at least a portion thereof is subjected to further cracking within the system under cracking conditions controlled independently of those employed in heating coil I. lnY the apparatus here illustrated, provision is therefore made for'removing selected relatively7 .low-boiling fractions of the reflux condensate from a suitable intermediate point in fractionator I3 and directing the same through line I9 =and valve to pump 2| by means of which they are supplied through line 22 and valve 23 to conversion in heating coil 24.

Furnace 25 supplies the required heat to the Vrelatively low-boiling oil passing through heating coil'24 to heat the same to the desired cracking temperature, which is preferably somewhat higher than that employed in heating coil I. A substantial superatmospheric pressure is also preferably maintained in heating coil 24 and a `regulated portion or all of the highly heated products from this zone may be directed, when desired, through line 2S and valve 21 into reaction chamber 5 wherein they are further cracked in' commingled state with the heated products 75l supplied to this zone, as previously described, from heating coil I.

Fractionation may be so controlled in fractionator I3 that the resulting vaporous products which remain uncondensed in this zone consist substantially only of materials boiling within the range of gasoline and normally gaseous products, or, when desired, these vapors may include materials of a somewhat higher boiling nature than gasoline such as, for example, heavy naphtha fractions, kerosene, kerosene distillate, pressure In the latter case, however, any such higher boiling fractions included with the vaporous product removed from fractionator I3, are of such a nature that they may be further cracked to produce additional yields of good antiknock gasoline under conditions suitable for reforming of the heavy gasoline components of the vapors to materially improve their antiknock value. These fractionated vaporous products are directed from the upper portion of fractionator I3 through line 30 and valve 3| to further fractionation in a secondary fractionator 32. The latter Zone, as here illustrated, is a separate fractionating column, although it may, when desired, take the form of an extension to fractionator I3.

The vaporous products supplied to fractionator 32 are separated in this zone by fractional condensation into relatively low-boiling vaporous components, consisting of light gasoline fractions of satisfactory antiknock value and normally gaseous products, and a higher boiling condensate consisting of or containing at least a substantial quantity of heavygasoline fractions of unsatisfactory antiknock value.

The low-boiling vapors which remain uncondensed in fractionator 32 are directed from the .upper portion thereof through line 33 and valve 34 to condensation and cooling in condenser 35. The resulting distillate and uncondensed gases pass through line 36 and valve 31 to collection and separation in receiver 38. The uncondensed gases may be released from receiver 38 through line 39 and valve 40 to storage or elsewhere, as desired. Distillate collected in receiver 38 is withdrawn therefrom through line 4I and Valve 42 to cooling and storage or to any desired further treatment and comprises the low-boiling gasoline fractions, produced as previously described, which are of satisfactory antiknock value.

When desired, regulated quantities of the distillate collected in receiver 38 may be returned therefrom to the upper portion of fractionator 32 as a cooling and refluxing medium by means of line 43, valve 44, pump 45, line 46 and valve 47. It is also within the scope of the invention to supply a suitable light distillate as a cooling and reiiuxing medium to the upper portion of fractionator I3, line 48 and valve 49 being provided in the case here illustrated for this purpose. The cooling and refiuxing medium thus supplied to the upper portion of fractionator I3 may comprise, for example, distillate from receiver 38 or, preferably, a distillate resulting from total or partial condensation of a regulated portion of the normally liquid lcomponents in the vaporous stream removed from the upper portion of fractionator I3.

The condensate separated, as previously described, in fractionator 32 from the vaporous products supplied to this zone is removed from the lower portion thereof and directed through line 5I) and valve 5I to pump 52 by means of which i1; isfsupphed through une 54 tozfurnher cracking or reforming 1in heating coil 6|, passing either through valve 55 in line54 or, allor :in part, through heat exchanger v58 by Ameans :of lines 56 and 59 controlled, respectively, byvalves 51 and A60. The function of heat exchanger 58 will be later explained.

The heavy gasoline fractions or heavy-gasoline@ containing condensate supplied to heating coil 6| is heated during its passage through this zone, by means of heat supplied from furnace 6l, to bracking conditions kof temperature and substantial superatmospheric pressure regulated to effect a material improvement in the antikn-ock value of saidgasoline fractions and to produce additional yieldsof goed quality gasoline from any higher boiling fractions of the condensate. The resulting highly heated products are discharged from heating coili through line 63, which preferably contains a pressure control valve 64, and preferably after being partially cooled to a lsufficiently low temperature to prevent any excessive further cracking thereof, are introduced into vaporizing and separating chamber 65. The desired cooling of these heated products is preferably accomplished, at least in part, by a lsubstantial reduction in the pressure imposed thereon as they pass through valve 64. Any required additional cooling may be accomplished in any well known vmanner suchy as, for example, by indirect heat exchange v' with one or more `relatively vcool intermediatel or inal products :of the process or charging stock therefor or by directly-comminglinga suitable cooling oil with the heated products passing through line 63. Meanscomprising lines 66 and valves-'61, l'

which will not be readily reduced to coke or oth'erobjectionable products in line v63.

Undesirable high-boiling products lsuch as heavy kpolymers and residual liquidare separated in chamber 65 from the vaporous components of the conversion products supplied to this zone and the heavy products thus separated from4 the vapors preferably include substantially all .of the 'r components of said conversion products which are not suitable for further cracking withinthe system to produce additional yields of gasoline. Preferably. controlled cooling is employed in .the

upper portion of chamber 65 to assist the de- 1 sired separation of vaporous and heavy .liquid products `and means will be later.` described .for supplying a suitable cooling medium' to this point VVof the system. l

In case chamber 65 is operatedv at a lower Ipressure or higher temperature, or both, relative Ato that employed in chamber '.8 andit .-isy desired to further vaporize and recover low-boiling fractions for further treatment from the residual liquid removed from chamber 8, the latter may be directed through line 68 and valve 69 into chamber 65 to undergo further vaporization "and separation in this zone and it may be supplied either directly to chamber 65 at 4anydesiredpoint in this zone or may be introduced lall or in part, by well known means, notillustrated, into line 63.

The heavy liquids which remain unvaporized in chamber 65 may be removed from the lower portion of this zone and directed through line 10 and Valve1l 'to Acooling andstorage or elsewhere, vas

desired. The `vaporous products from `chamber 65 are directed therefrom to fractionation in fractionator` 12 Whereingtheir components' boiling above therangepof the desired gasoline product of this stage of the system are condensed as'reflux condensate.. l

Fractionated vapors of the desired end-boiling point, which remain uncondensed-in fractionator 1,2, comprise the normally gaseous products of this stage of the process and gasoline of good antiknock. value, the latter preferably being of higher` end-boiling point than that recovered from receiver 38. These vapors are directed from the upper portion of fractionator 12 through line 13 andvalve 14 to condensation and cooling in condenser 15. The resulting distillate and uncondensed gases p ass through line 16 and valve 11 to collection and separation in receiver 18.

The uncondensed gases are released-from the receiver to storage or elsewhere, as desired, through line 19 and valve 80. Distillate is withdrawn from receiver 18 through line 8| and valve 82 to storage or to any desiredy further treatment. Regulated quantities of the distillate collected in receiver 18 may be recirculated by means of line 83, valve 84, pump A85, line 86 and valve 81 to the upper portion of fractionator 12 as a cooling and refiuxing medium.

The reflux condensate formed in fractionator 12- is removed from the lower portion of this zone through line 90 and valve 9| to pump 92 by means of which it is fed through line 93 and may be v,directed all or in' part, when desired, through line 94, valve 95, lin-ell, valve |02 and line, |08 into fractionator I3 at any desired point Vin this zone wherein it commingles with the vaporous products undergoing fractionation therein, serves as a cooling and refluxing medium for the vapors and is at least partially vaporized and subjected to fractionation therewith. Preferably, however, useful heat is extracted from thev reflux condensate formed in fractionator 12 to preheat and/or reboil the condensate supplied from fractionator 32 to heating coil 6|. Preheating of said condensate from fractionatorv 32 may be raccomplished by passing all or a regulated portion of `the 4 reflux condensate from fractionatory 12 through valve 96 in line 93 into and through heat exchanger 58 in indirect heat exchange with the condensate fromv fractionator f 32 and thence through line 91 and valve 98 into line |0|. Reboiling of the condensate formed in fractionator 32, whereby to substantially free the same of dissolved gases and other undesired low-boiling components, may be accomplished by diverting regulated quantities of the reflux condensate from line |02 through line |03 and valve |04 into and through a suitable closed coil or heat exchanger |05 in -indirect heat exchange with the condensate in the lower portion of fractionator 32 and thence through line |06 and valve |01 into line |08. This Vreboiling may, when desired, be accomkplished in a zone of any well known form, not

lboth of the manners described, it not only serves the useful purpose mentioned of preheating and/or` reboiling the condensate from fractionator 12, but will also function as a more efiicient vcooling and refluxing medium in fractionator I3.

The inventionl also contemplates the useV of 'ployed.

regulated quantities of the reflux condensate formed'V in'fractionator 12 as a cooling vand refluxing medium in theupper portion of chamber 65. This is accomplished in the case here illustrated by diverting regulated quantities of the reflux condensate from line IIlI, through line |09, valve I I0, cooler III, line II2 and valve I|3 into the upper portion of chamber 65 wherein it preferably is intimately contacted by means of a suitable spray, baffles, perforated pans, bubble trays or the like, not illustrated, with the vaporous products in this zone of the system, serving to partially cool the same and remove undesirable high-boiling components therefrom, so that only relatively clean vapors suitable for further cracking in heating coil 24 and/or I are supplied from chamber 65 to fractionator 12.

Reflux condensate from fractionator 12 may also be introduced into line 63, by well known means, not illustrated, through one or both of the lines 66 and valves 61, to serve as a cooling medium for the hot conversion products discharged from heating coil BI prior to its introduction into chamber 65 and, when reflux condensate from fractionator 12 is thus utilized, it may be supplied to line 63 directly from pump 92 or from heat exchanger 58 or from cooler I I I or a similar cooler, by well known means, not illus- 4trated.

When heating coil 24 is utilized, the invention also contemplates the introduction, when desired, of a regulated portion or all of the highly heated products from this zone, with or without prior cooling to any desired degree, into chamber 65 instead of into reaction chamber 5. Provision is made in the case here illustrated for diverting regulated quantities of these products from line 25 through line |4 and valve I I5 into line 63 and thence to chamber 65, although products from heating coil 24 may be separately supplied, with or without prior cooling,to chamber 65 at any desired point in this zone, by well known means, not illustrated.

Charging stock for the process is supplied through line IIG and valve ||1 to pump I I8 by means of which it is directed in any one or any desired combination of several alternative but non-equivalent manners of treatment within the system. The point or points at which the charging stock is introduced into the system may be selected to suit the type of charging stock em- In case it is an oil of relatively wide boiling range, such as crude petroleum, topped crude or the like, containing a substantial quantity of both relatively low-boiling and high-boil- A ing components, and in case heating coil 24 is employed, the charging stock is preferably directed from pump IIS through line I I9 and valve I2U into fractionator I3, wherein it commingles with the relatively hot vaporous conversion products undergoing fractionation in this zone and is separated therewith into relatively low-boiling and high-boiling fractions for treatment in the respective heating coils 24 and I. The charging stock is also preferably supplied to fractionator I3 in case it contains any low-boiling gasoline fractions of satisfactory antiknock value, so that the latter may be vaporized in fractionator I3 and recovered as a portion of the overhead product from fractionator 32. The charging stock may be supplied to fractionator I3 in any case except when it contains low-boiling fractions which would contaminate the overhead product 4from fractionator 32 if commingled therewith and, in any case, may, when desired, be preheated to below cracking temperature by any Well known means, not illustrated, prior to its introduction intotthe fractionator. However, in case the charging stock is an oil of relatively high-boiling characteristics, or in case heating coil 24 is not employed, it may be supplied all or in part directly to heating coil I by means of lines |2|, |22, |23, valve |24 and line I1. When heating coil 24 is employed and the charging stock is an oil of relatively low-boiling characteristics suitable for cracking in this zone, it may be supplied all or in part directly to heating coil 24 by means of valve |25 in line |22 and line 22. In case the charging stock does not contain materials of unsatisfactory antiknock value which boil within the range of the reformed gasoline product, it may be supplied all or in part by means of valve |26 in line |2| to fractionator 12 to commingle therein with the vaporous products undergoing fractionation in this zone, assisting their fractionation and being subjected to fractionation therewith. In the latter case the total charging stock, or high-boiling components thereof which remain unvaporized or are condensed in fractionator 12, are supplied therefrom, together with the reflux condensate formed in this zone, to fractionator I3, in the manner previously described, and thence to cracking in heating coil 24 and/or heating coil I.

The process herein disclosed is well adapted to the treatment of a secondary charging stock whichmay comprise distillate such as straightrun gasoline, pressure distillate or cracked gasoline from another cracking operation or any other relatively low-boiling oil consisting primarily of gasoline boiling range materials and containing both low-boiling gasoline fractions of satisfactory antiknock value and higher boiling gasoline fractions of unsatisfactory antiknock value. Provision is made in the case here illustrated for supplying such secondary charging stock through line |21 and valve |28 to pump |29 by means of which it is fed through line |30 and may be introduced all or in part through line |32 and valve |33 directly into fractionator I3, wherein it commingles with the hot vaporous conversion products undergoing fractionation and is substantially vaporized, the vaporized gasoline components passing from fractionator I3, together with the cracked gasoline vapors from this zone of the system, through line 30 and valve 3| to further fractionation, as previously described, in fractionator 32. Provision is also made in the case here illustrated for preheating the secondary charging stock prior to commingling the same with the vaporous conversion products undergoing fractionation by directing the same through valve I3| in line |30 into and through heat exchanger |34, wherein it passes in indirect heat exchange with the relatively hot vaporous conversion products undergoing fractionation in fractionator I3 and wherefrom it may be thence directed through line l|35 and valve |36 directly into fractionator I3 at a point y beneath heat exchanger I 34. In case the secto' beingA commngled' with the vaporous' products preheated secondary charging stock. from heat exchanger I34 through line |35, line .I3'|', valve |38 and 'line 30 into' fractionator 32.

-In addition to the provisions' previously de:- scribed for partially cooling relativelynhot'conversion products at` various: points in the system,.the invention contemplates partially cooling the heated products supplied from .chamber .to chamber'. 8, to arrest or retard theirfurther cracking, by commingling a suitable cooling oil therewith in line B on either or both sides rof the pressure reducing valve 1, lines I4ifc'ontaining control valves I4! being' provided for lthis purpose. Provision isl also madev for utilizing a suitable cooling and refluxing medium .in the.

upper portion of chamber 18 and line` I42 controlled by valve I 43 is provid'edfor the introduction of a suitable cooling and refluxing medium into this zone. The coolingk medium .thus utilized in line 6 and/or the vupper 'portion of chamber 8 may comprise, for example, regulated quantities lof all or a selected fraction ofthe reflux condensate formed in fractionat'or I3,or the reflux condensate formed in fractionator T2, or .regulated quantitiesv of: the charging stock supplied to the system.

The preferred range of operating conditions which may be employed within the scope of the invention, to accomplish the 'desired' results in an apparatus such as illustrated and above described, may be approximately as follows: Heating coil I may employ a conversion ternperature, measured at the outlet therefrom.'

ranging, for example, frorn850 to 950 F., or thereabouts, preferablywith a superatmospheric pressure at this point in the system of from 1'00 to 500 pounds, or thereabouts, per square inch. Heating coil 24, when utilized, preferably employs a. higher cracking temperaturev than 'heating coil I, the preferredrange, as measured at the outlet of heating coil 24, being-'from 900 to 1000* F., or more, preferably With .a superat'mospheri'c pressure at this point in the system of from 200 to 800' pounds, or thereabouts, per square inch. `Any desired superatmospheric pressure no greater than that employed at the outlet of the communicating heating vcoil utilizing the lowest pressure may be yemployed in reaction chamber 5, the preferred range bechamber 8, fractionator 32 being operated, when desired, at an appreciably lowerr pressure rthan that employed in fractionator I3.A .Heating coil 6I preferably employs an outlet *temperature within the range of 925 to 1050 F. orzmore, preferably with a superatmospheric pressure at this point in the system which. may'v range as high as 1000 pounds, or more, per square inch. The products suppliedv from heating coil 24 and/'or heating coil 6I to chamber 65 are preferably cooled to a, temperature of the order of 600 to 800 F., prior to theiry introduction intozthis: zone, and their vaporous components may be further ."cooled within' 'chamber 65.. When residual' vliquid fromchamben is supplied to .chamber 65 the latter zone is preferably operatedr at a lower pressure or. higher' temperature, 'or both,'with respect to the temperature and pressure condition's employed in vaporizing and separating .chamber 8".. Thepressure employed in? chamber 615, whichis preferably of the 'order of100 pounds or more; per square inch, superatmospheric, down to .substantially atmospheric. pressure, maybe .substantially equalized orreduced in the succeeding fractionating, condensing and collecting equipment. 'z

Asa specific example of an operation of the process as it may be conducted in an apparatus ofthe character illustrated and above described: Thecharging stock is a Montana crude of about 32? AJP'. I'.- gravity which contains approximately 26% of'straig'ht-'run gasoline boiling upto 437 The charging'stock is supplied to' fractionator" |31 wherein it is separated, together with the vaporous conversion products supplied to this zone, intoan overhead vaporous fraction having an end-boiling'point of approximately550 F., an intermediate fraction having an yinitial boiling point. of'approximately 300 F. and an endpoint-'of approximately-630 F. and a heavy -liquid; fraction having an .initial boiling point of approximately 320' F. and containing approximately 35%. of material boiling up to 600 F. Said; high-boiling fraction is heated in heating coil I; toan outlet temperature of approximately 910' ata superatmospheric pressure of approximately 300 .pounds per square inch. The intermediate liquid. fraction is supplied to heating coil 24lwherein itis heated to a cracking temperature of approximately 950 F. at a superatmospheric pressure of approximately 350 pounds per". square inch. The hot conversion products from heating coils I and v24 are supplied to reactionzchamber 5`which is maintained at a superatmospherie. `pressure of approximately 300 poundsy per squarey inch. Vaporizing and separating. chamber 8,. to which the total vaporous and `liquid products from. chamber 5 are supplied in commingled state, ismaintained at a superatmospheric pressure ofy approximately l20fpounds per square. inch, residual liquid from this zone being supplied to' chamber 65,. while the vaporous productsv are directed to fractionator I3. The overhead Vaporous stream from fractionato-r I3 is .supplied to secondaryfractionator 32 and a secondary charging stock, comprising pressure distillate fro-m an external source having an initial boiling point of approximately F; and an end-boiling point'fof approximately 560 F., 'is also-introduced into `fractionator 32 lafter being first.: preheated, by indirectk heat. exchange with the' vaporous products undergoing fractionation inifractionator I3, to a temperature of opproximately 400 F. TheA overhead vaporous product fromfractionator 32 has an end-boiling point. of approximately 370 F. and a light gasoline of apprbximatelyv this vend-point is condensed and separated from the normally gaseous products.` The 'bottoms removed from fractionator 32 have an initial'boiling'point of Aapproximately240" F. and an end-boiling point of approximately 560 F. Thismaterial is subjectedr in heating coil 6I vto a conversion temperature of approximately 980 F. at a 'superatmospheric pressure of about "400 pounds per square-inch, as measured at the out-v are further cooled in chamber 65 by'coolirig and recirculating reiiux condensate from fractionator 32 to the upper portion of this zone. A reformed gasoline of approximately 400 F. endboiling point is recovered from fractionator 12 as the overhead product and residual liquid is recovered from the lower portion of chamber 65. Reflux condensate formed in fractionator 12, which has an initial boiling point of approximately 375 F. and an end-boiling point of approximately 650 F., is in part cooled and returned to the upper portion of chamber 65, While the remainder is utilized as a reboiling medium for the bottoms from fractionator 32 and is thence introduced into fractionator I3.

The above described operation Will yield, per barrel of total charging stock (which consists of approximately 70% crude oil and approximately 30% pressure distillate), approximately 75% of gasoline having an antiknock value of better than 70 by the motor method and approximately 14% of heavy fuel oil recovered as residue from chamber 65, they remainder being chargeable principally to uncondensible gases.

I claim as my invention:

1. A process for the pyrolytic conversion of hydrocarbon oils which comprises cracking an oil of higher boiling characteristics than gasoline at substantial super-atmospheric pressure in a heating coil and separating the resulting vaporous and liquid conversion products, fractionating the vaporous conversion products, to condense therefrom as reflux condensate components boiling `above the range of gasoline, supplying reflux condensate formed by said fractionation to the heating coil for cracking therein, subjecting resultant fractionated vapors to further fractionation in a second fractionating step and commingling with the vapors supplied to said second fractionating step distillate from an external source which contains at least a substantial quantity of low-boiling gasoline fractions of good antiknock value and a substantial quantity of higher boiling gasoline fractions of inferior antiknock value, separating the commingled materials in said second fractionating step into lowboiling vaporous components consisting predominantly of light gasoline fractions of satisfactory Iantiknock Value and a higher boiling condensate comprising low antiknock high-boiling gasoline fractions of said distillate and of the cracked vapors, subjecting said low-boiling vaporous components to condensation and recovering and separating the resulting light gasoline distillate and uncondensed gases, reforming said higher boiling condensate formed in the second fractionating step to produce therefrom high yields of good antiknock gasoline by heating the same to a high cracking temperature at substantial superatmospheric pressure in a separate heating coil, partially cooling the resulting highly heated products and separating the partially cooled materials into vapors and heavy non-vaporous components, fractionating the last named vapors out of contact with the vaporous products in the aforementioned fractionating steps to condense therefrom as reflux condensate components boiling above the range of the desired reformed gasoline product, passing reflux condensate formed in the last described fractionating step in direct heat exchange with said higher boiling condensate prior to the reforming of the latter and then returning the reflux condensate to the rst mentioned fractionating step in liquid form to serve as a refluxing medium in said first-mentioned fractionatingstep, and subjecting fractionated vapors of the desired end-boiling point lfrom the last described fractionating step to condensation to recover therefrom a reformed gasoline'of good antiknock value and of'higher end-boiling point than said gasoline distillate recovered from 'the second mentioned fractionating step,

2. A processsuchas dened in claim 1 Wherein said distillate' from an external source is passed in indirect heat exchange with the vaporous products undergoing fractionation in .the first mentioned fractionating step prior to commingling with the` vaporous products subjected to said further fractionation'in the second fractionating step.

3. A process such as defined in claim 1 wherein said distillate from an external source is partially vaporized by passing the same in indirect heat exchange with the vaporous products undergoing fractionation in the rst mentioned fractionatingstep, the resulting heated and partially vaporized distillate thence directly commingled with the vaporous products in the first mentioned fractionating step and only its resultant vaporized components subjected to further fractionation in the second fractionating step.

4. A process such as dened in claim 1 Wherein regulated quantities of the reflux condensate formed inthe last described fractionating step are cooled and thence commingled with relatively hot products of the reforming step'to assist said partial cooling and separation thereof.

5. A process such as defined in claim 1 Wherein regulated quantities of the reflux condensate formed in the last described fractionating step are cooled and commingled with vaporous products of the reforming step `prior to said fractionation of the latter.

6. A conversion process which comprises cracking hydrocarbon oil heavier than gasoline, and separating resultant vapors from residue, fractionating the vapors to separate therefrom a reflux condensateheavier than gasolinega light gasoline vapor and an intermediate condensate containing the heavy gasoline fractions, returning s aid reux condensate to the cracking operation, iinally condensing and collecting said light gasoline vapor, reforming said intermediate condensate by subjection to cracking conditions in dependently of the-rst-mentioned oil, vfractionating theA vaporous products yof the reforming step independently of the first-namedy vapors,l passing resultant reflux condensate in indirect heat exchange With said intermediate `condensate prior to supplying the latter to the reforming step, then introducing the last-mentioned reflux condensate into contact with the rstnamed vapors undergoing fractionation to serve as a reuxing medium for these vapors, and finally condensing the vapors uncondensed by the fractionation of said vaporous products of the reforming step.

7. A conversion 'process which comprises cracking hydrocarbon oil heavier than gasoline, fractionating `the resultant vapors to condense fractions thereof heavier than gasoline and re-l turning fractions so condensed to further cracking Within the system, further fractionating theV vapors to separate `the same into light gasoline fractions of satisfactory anti-knock value and a higherboilng condensate comprising low antiknock heavy gasoline fractions, condensing and recovering said light gasoline fractions, subjecting said condensate to reforming tov increase the and collecting the reformed vaporous products uncondensed in the third-mentioned fractionating step.

8. The process as deiined in claim 7 further characterized in that said higher boiling condensate is reboiled during its indirect heat exchange with said reflux condensate to free it of good anti-knock low-boiling gasoline fractions prior to the reforming thereof.

LYMAN C. HUFF. 

